RU2642503C2 - Method of characterizng part manufactured from composite material - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: characteristics of the longitudinal ultrasonic wave passing along the path inside the part are determined, while measuring the transit time of the longitudinal ultrasonic wave transmitted by the part and measuring the transit time of the transmitted wave by observing the wave beginning.

EFFECT: providing the ability to quickly and reliably determine the parameters of parts made of the composite material.

5 cl, 10 dwg

Description

FIELD OF THE INVENTION

The invention is in the field of methods for characterizing parts made of composite material in mechanical engineering, in particular in the aircraft industry.

State of the art

Along with the fact that a given part is being developed, it is necessary to know the fiber content and the resin content in a given area of the part. To do this, as is known, the velocity of propagation and attenuation of a longitudinal ultrasonic wave passing through the part is measured.

One way to measure these values is to use an ultrasonic transducer in transceiver mode. Attention is then paid to the area of the part, which is defined by mutually parallel, front and rear surfaces. The longitudinal wave is directed so that it propagates perpendicular to two surfaces, partially reflecting and, also, attenuating in the material of the part. Thus, the first signal (echo) coming from the front surface is observed, as well as the second signal (echo) coming from the back surface, called the reflected signal. The converter receives the reflected wave, and then, by observing the two reflected components, it is possible to trace both the propagation velocity and the attenuation of the wave in the material.

Nevertheless, such a solution is unsuitable for materials that strongly absorb ultrasonic waves. This applies, for example, to three-dimensional 3D fabric composites with a structure that is inhomogeneous and anisotropic. For details of industrial thicknesses, no reflected signal is seen in the recordings made on such materials due to strong absorption.

Thus, it is necessary to develop a method suitable for application to parts made of composite materials, and making it possible to characterize a large number of parts, regardless of their thickness or their absorption essence.

Disclosure of invention

The invention relates to a method for characterizing a part made of a composite material, the method including the step of determining the transmission characteristics of a longitudinal ultrasonic wave along the path inside the part, and differs in that it measures the propagation time of a wave transmitted by the part.

Using this technology, the problem associated with the absence of a reflected signal in the measurements in the transceiver mode is overcome.

According to an advantageous characteristic, the transmission time of a transmitted wave is measured by observing the beginning of the wave.

Using this characteristic, it is possible to ignore significantly enhanced problems of phase shift and deformation of the sinusoidal signal of the ultrasonic wave used, caused by thick materials, or caused by the complex inhomogeneous and also anisotropic structure of certain composite materials.

In the implementation, the propagation velocity of the longitudinal ultrasonic wave passing in the part is determined.

This provides information that is useful for determining the fiber content and resin content in the composite material, information that can be used in the development of the investigated part.

In another embodiment, which may be combined with the previous embodiment, the amplitude of the transmitted wave is also measured in order to determine the attenuation along the entire length or unit of length to which the longitudinal ultrasonic wave is subjected when passing through the part.

This provides information that is useful for determining the pore content, which can be used in the development of the investigated part.

Preferably, the propagation time of an ultrasonic wave transmitted in the absence of the part is measured as the propagation times of ultrasonic waves reflected respectively by the first front side of the part and the second front side of the part in order to determine the size of the part by letting the longitudinal ultrasonic wave pass along the path into the part.

With this characteristic, which is optimal, only advantageous, an accurate measurement gets the size of the part through which the transmitted wave passes, and this size is quite variable in parts made of composite material, so it can be useful to know the exact value for of this part, for a particular path followed by the ultrasonic wave used.

In particular, the method is carried out for a part made of 3D fabric composite material.

Such materials are especially promising for characterization because of their inhomogeneity and because of their anisotropy. Using the invention, it is possible to investigate them quickly and reliably, especially when the details are in development.

Brief Description of the Drawings

FIG. 1 shows a preliminary action in the context of implementing the method of the invention.

FIG. 2 shows three stages of a thickness measurement step carried out in the invention.

FIG. 3-5 show signals recorded during the three stages of FIG. 2.

FIG. 6 shows the step of observing a transmitted wave during the method of the invention.

FIG. 7 shows a signal measured during the step of FIG. 6.

FIG. 8-10 show the signals obtained during the steps of FIG. 2-6 for a spacer made of composite material.

The implementation of the invention

As shown in FIG. 1, two flat ultrasound transducers operating in transmission mode are set to a straight line. This alignment on one straight line constitutes the preliminary stage E0. The sensors are separated by a liquid, such as water. The converter 10 operates in a radiation mode, and the sensor 20 in a reception mode. The signal received by the sensor 20 passes through a maximum after successive adjustments of the Oy and Oz axes, as well as the angles θ and ϕ.

In FIG. Figure 2 shows a measurement of the thickness of the material of the test piece, labeled 30. This measurement should be accurate to one micrometer.

The first stage E1 consists in measuring the propagation time of a wave passing through water between two transducers 10 and 20, in the absence of a part. The second stage consists in measuring the propagation time of the wave reflected by the first front surface designated 31, part 30, by a transducer 10 operating as a transceiver facing the surface 31. The third stage consists in measuring the propagation time of the wave reflected by the second surface, designated 32, part 30 , the Converter 20, working, in turn, as a transceiver, and facing the surface 32.

The propagation time is measured in each case by observing the beginning of the signal, and not the arc of the signal. This makes it possible for the operator to ignore any phenomenon associated with a possible phase shift of the signal. Specifically, in the presence of many reflections, phase shifts appear. This also happens when, after reflection, the signal changes direction. The shape of the signal arcs is modified, and it is difficult to obtain the exact value of the propagation time. That is why it is proposed to measure the signal by observing exclusively the beginning of the signal.

Since the wave propagation velocity V _water in the water is known, it is possible to obtain by subtracting the thickness of the part of the steps El, E2 and E3, using the formula X ₂ = (t _{X1 + X2 + x3} t _X3- t _XL) × V _water, where X1 is the distance between transducer 10 and surface 31, X2 is the thickness of the part at the point of beam exposure, and X3 is the distance between transducer 20 and surface 32, and where t _{X1 + X2 + X3} , t _Xl and t _X3 are the transit times measured during stages E1, E2 and E3, respectively.

FIG. 3-5 show graphs displayed during stages E1, E2 and E3, respectively, with water at 22 ° C, a wave with a frequency of 5 megahertz (MHz) (giving a propagation speed of 1486.45 meters per second (m / s) in water ), for a spacer having a thickness of 76.20 millimeters (mm) and made of titanium TA6V. The wave propagation time is measured based on the start of the wave given by the corresponding references 100, 119 and 120.

The following results were obtained:

t _{X1 + X2 + X3} 92.72 microseconds (μs)

t _X3 = 2,98 / 2 = 26.49 ms

t _Xl = 26.49 / 2 = 14.97 μs

X2 = (t _{X1 + X2 + X3} -t _X3 -t _X1 ) V _water

X2 = (92.72 10 ^-6 - 26.49 10 ^-6 - 14.97 10 ^-6 ) 1486.54

X2 = 76.20 mm

The thickness measured by the thickness gauge is actually 76.20 mm, i.e. 3 ".

FIG. 6 shows a step E4 during which a wave transmitted by part 30 is observed. Thus, the transducer 10 is operating in a radiation mode, while the transducer 20 is operating in a receiving mode. The incident wave is indicated by 40 in the figure, the wave propagating in the part 30 is indicated by 41, and the transmitted wave is indicated by 42.

The wave propagation time in the part 30 is expressed as t ' _X2 = t- (t _X1 + t _X3 ). Knowing X2, as defined in advance, the wave propagation velocity in the material is expressed as V _material = X2 / t ' _X2 .

FIG. 7 shows the signal observed during stage E4 for a spatial spacer 76.20 mm thick made of titanium (TA6V), even with a wave at 5 MHz. The wave propagation time is measured based on the start of the wave indicated by 130.

The values obtained are as follows:

t = 53.80 μs

t ' _X2 = (53.80 10 ^-6 - 26.49 10 ^-6 - 14.97 10 ^-6 )

t ' _X2 = 12.34 μs

V = 76.20 10 ^-3 / l2.34 10 ^-6

And, in the end, the numerical value of the velocity is V = 6175.04 m / s. This value is confirmed using a conventional measurement of the propagation velocity in order to verify the reliability of the results of the method.

FIG. 8-10 show the scans obtained for stages E2, E3, and E4 for a composite stepped spacer having a thickness of 47.09 mm with transducer radiation from 1 MHz. The wave propagation time is measured based on the wave beginnings given by the corresponding references 140, 150 and 160.

The values obtained are as follows:

t _{X1 + X2 + X3} = 90.22 μs

t = 74.90 μs

t _X3 = 52.42 / 2 = 26.41 μs

t _Xl = 64.68 / 2 = 32.34 μs

X2 = (t _{X1 + X2 + X3} -t _X3 -t _X1 ) V _water

X2 = (90.22 10 ^-6 - 26.21 10 ^-6 - 32.34 10 ^-6 ) 1486.54

X2 = 31.67 10-6 1488.76

X2 = 47.078 mm

t ' _X2 = t - (t _X1 + t _X3 )

t ' _X2 = (74.90 10 ^-6 - 26.21 10 ^-6 - 32.34 10 ^-6 )

t ' _X2 = 16.35 μs

V _composite = X2 / t ' _X2

V _composite = 47.078 10 ^-3 / 16.35 10 ^-6

And, in the end, the numerical value of the velocity is V _composite = 2879.4 m / s.

Then attention is paid to the attenuation of the longitudinal wave in the material.

The expression for the amplitude of the wave transmitted from the emitter to the receiver is written as follows: Y ₁ = A _max e ^- α ^{1 (X1 + X2 + X3} ), where A _max represents the maximum amplitude on the surface of the transducer, and α ₁ represents the attenuation of the wave in water.

The expression for the amplitude of the wave transmitted from the transmitter to the receiver after passing through the material is recorded as the following: Y ₂ = A _max e ^- α ^{1 (X1 + X3)} e ^- α ^2X2 t ₁₂ t _21, wherein α ₂ is the wave attenuation in material, t ₁₂ is the coefficient of amplitude transmittance from water to material, and t ₂₁ is the coefficient of amplitude transmittance from material to water.

The expression for the product t ₁₂ t ₂₁ is a function of the acoustic impedance of the material Z ₂ = ρ ₂ V ₂ and the acoustic impedance of water Z ₁ = ρ ₁ V ₁ . In terms of acoustic impedance, ρ represents the density and V represents the propagation velocity of the longitudinal wave with the frequency discussed.

The amplitude ratio Y ₁ / Y _{2 is} written as follows:

From which it is possible to derive an expression for attenuation in a material:

The first embodiment relates to a spacer made of a composite material having a thickness of 47.09 mm using a wavelength of 2.25 MHz.

The numerical values for this implementation are as follows:

ρ ₂ = 1525, 71 kilograms per cubic meter (kg / m ³ )

V ₂ = 2946.75 m / s

Z ₂ = 4.39316 megaohms on alternating current (MΩac)

ρ _water = 997.77 kg / m ³

V _water = I486.54 m / s

Z _water = 1.48322 MΩac

t ₁₂ t ₂₁ = 0.75478

X ₂ = 47.078 mm (accurate ultrasonic measurement)

Y ₁ = 643.2 millivolts (mV)

Y ₂ = 15.885 mV

α _water2.25MHz = 0.972 neper per meter (Np / m)

α ₂ = 73.61 H / m.

The second embodiment relates to a spacer made of a composite material having a thickness of 47.09 mm using a wavelength of 1 MHz.

ρ ₂ = 1525.71 kg / m ³

V ₂ = 2879.39 m / sec

Z ₂ = 4.39311 MΩac

ρ _water = 997.77 kg / m ³

V _water = I486.54 m / s

Z _water = 1,48322 MΩac

t ₁₂ t ₂₁ = 0.75479

X ₂ = 47.078 mm (accurate ultrasonic measurement)

Y ₁ = 370.25 mV

Y ₂ = 16.395 mV

α _water1MHz = 0.682 Np / m

α ₂ = 60.92 Np / m.

The invention is not limited to the described implementations, but extends to any option within the scope of the claims.

Claims (5)

1. A method for characterizing a part made of composite material (30), the method comprising the step of determining the characteristics of a longitudinal ultrasonic wave (41) passing along a path inside the part (30), and differs in that (E4) the transit time of the longitudinal ultrasonic wave is measured (42) passed by the part (30), and the transit time of the transmitted wave (42) is measured by observing the beginning of the wave (130, 160). 2. The characterization method according to claim 1, wherein the propagation velocity of the longitudinal ultrasonic wave (41) in the part (30) is determined after passing the path in the part (30). 3. The characterization method according to claim 1, in which the amplitude of the transmitted wave (42) is also measured to determine the attenuation along the entire length or unit of length to which the longitudinal ultrasonic wave (41) is exposed when passing through the part (30). 4. The characterization method according to claim 1, further comprising the step of measuring (E1) the propagation time of the ultrasonic wave that passed in the absence of the part, and the measuring step (E2, E3) of the propagation time of ultrasonic waves reflected respectively by the first front side (31) of the part and the second the front side (32) of the part to determine the size of the part (30), when a longitudinal ultrasonic wave (41) is passing along the path into the part. 5. The method of characterization according to claim 1, carried out for parts made of 3D fabric composite material.

Images